Welcome to the board from Southern California!!

I have a 630. Had been looking at the 640 but had a lot of people tell me that if I mainly use it for quilting that it is harder to maintain a 1/4" seam with the wider feed dogs.
I know that you can just move the needle but I like using the 1/4" foot to sew with. I have the BSR and an embroidery module. Love my machine!

I find it easy to get a perfect 1/4" on my 440 (5.5mm) It takes more effort with my 820 (9mm). But other quilters say they have no trouble at all, so you have to try it for yourself. Of course, test drive your final candidates for purchase with the fabrics, threads, and needles you prefer. Bring blocks to piece, mini quilt sandwiches to quilt, and anything else you typically do, the more challenging, then better.

Since she wants the BSR she's going to have to go with a Bernina :> Just putting that out there to those who try to talk her out of it. I own many different brands of sewing machines and Bernina is by far the highest quality machine on the market. If cost isn't a huge factor, I'd go with the 730.

I have the 830 and 9mm stitching. No problem finding the 1/4" sweet spot!

730 all the way! Since they came out with the 800 series, you may be able to get a discount or even a gently used one. I bought mine used and have no regrets! Buying used from a dealer allowed me to have a much nicer machine!

I appreciate all of the replies. I should have elaborated further and stated that I have only sewn 2 quilts but thoroughly have been bitten by the quilting bug. I see many more quilts in my future and I am also interested in sewing my own clothes. Now, that being said, I would really like to purchase a bernina as my current machine is an inexpensive simple machine that is rather limiting but has been great for a beginner. Sooo, I went looking at the Bernina's and narrowed it down to the 3 (450, 640, 730) but I don't want to bite off more than I can chew. This is why I am looking for some good advice. Thanks.
P.S. I like the embroidery component but do not necessarily have to have it.